Magnetic holding-table for metal-working machines.



No. 687,93l.

M. BARR.

MAGNETIC HOLDING TABLE FOR METALWORKING MACHINES. (Application mea Aug. 6, 190m (No Model.)

Patented Dec. 3, |901.

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MWI/ MW UNITED STATES PATENT OFFICE.

MARK BAER, OE BROADIIEATI-I, ENGLAND, AssIeNOR rro TI-IE LINOTYPE COMPANY, LIMITED, OE LONDON, ENGLAND.

MAGNETIC HOLDING-TABLE FOR METAL-WORKING MACHINES.

SPECIFICATION forming part of Letters Patent No. 687,931, dated December 3, 1901.

Application led August 6,1900.

To all whom it may concern:

Be it known that I, MARK BARR, of Broadheath, in' the county of Chester, lngland, have invented certain new and useful Improvements in Magnetic Holding-Tables for Metal-Working Machines; and Ido hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to improvements in magnetic holding-tables for metalworking machines, and is especially appli'- cable to holding flat metal articles down upon such tables.

It consists in certain novel improvements which make the table simpler, more efficient, and cheaper than those hitherto known, which improvements are hereinafter described at length and claimed.

Referring to the accompanying drawings, which are to 'be taken as part of this specification and read therewith, Figure 1 is a plan of an improved table after a corner of its top has been broken away to show the interior, having a flat brass plate held down upon it; Fig. 2, a sectional side elevation corresponding with Fig. l; Fig. 3, a plan, and Fig. 4 a side elevation, of a holding-cam.

lis the article to be held. It may be of any material, shape, or size; but it must be iirmly mounted upon a flat iron or steel plate 2 of an area not smaller than its own and thick enough for the holding-cams to bear against. The plate 2 is preferably flat to rest evenly upon the table-top 3, for the iiatter it is the greater will be the number of holdingpoints between it and the said Itop. It is of iron or steel, because of the superior magnetic properties of these metals. The tabletop 3 is iiat and of brass, because that metal is not magnetic. It iits down upon a box 4. The material of this box is iron or steel, because of the magnetic properties of these metals. Within the box 4 are arranged two series of magnetic poles 5 6 in such a way that each pole of one seriessayseries 5-is N to all the poles of the other series G, which are consequently S to it. Accordingly only alternate poles 5 are wound, the poles of the other series 6 being unwound.

It is a mat- Serial No. 26,074. (No model.)

ter of indifference whether the poles of the series 5 are wound in parallel or series so long as the winding` 7 is continuous throughout the series. The pole-pieces of both series are screwed or otherwise made fast in the bottom of the box l without being insulated therefrom, standing up straight within the said box, as shown in Fig. 2, and presenting their top ends through the'brass tabletop 3, with the top surface of which they are flush, as shown.

As soon as the current is switched into the windings 7 the coils 5 are energized, and magnetic currents pass from each pole 5 to each pole 6 or from each pole 6 to each pole 5,according to the direction of winding and current, and as the poles 5 and 6 alternate each other in directions parallel with the sides and ends of the box the magnetic nx is of equal intensity in vevery direction. When the plate 2 is laid upon the top 3, it will touch a certain number of pole-pieces 5 and 6 and so form a part of a corresponding number of magnetic circuits, which Will hold it down upon the said top 3 accordingly. At the same time the plate 2 can be moved over the top 3 in any direction, and to prevent such motion when it is not wanted holding-cams 3 are provided. A cam 8 has a head 9, with a notch 10 across it on the top side ot' it and a pin projecting from the bottom side of it. 12 12 are a series of holes in the table-top 3 clear of the poles 5 and 6, in which the cam-pins 1l can fit and turn. These holes l2 are preferably in rows between the rows of poles, as shown in Fig. l, and the cams 8 of a sufficient eccentricity to bear against the edge of the plate 2 when they are turned on their pins toward it by a screwdriver inserted in the notches lO.

I claim- 1. The hereinbefore-described combination of box of magnetic material; cover of nonmagnetic material; series of wound polepieces electrically connected with the box; series of unwound pole-pieces electrically connected with the box and both flush with the top surface of the box-cover; and continuons winding on all the wound pole-pieces.

2. The hereinbefore-described combination of box of magnetic material; cover of nonmagnetic material; series of wound pole- IOO my invention l have signed my name in prescnce of two subscribing Witnesses.

MARK BARR.

Witnesses:

ROBERT E. MCLAREN, CHAS. S. WooDRoFFE. 

